The program area, located on Java Island and covering a total of about 13,000 km2, is a cluster of river basins consisting of: (i) the 6,600 km2 Citarum river basin which straddles the central part of the program area and flows from south to north into the Java Sea; (ii) the 4,400 km2 cluster of small basins whose drainage areas are connected to the Citarum river system through the East Tarum Canal; and (iii) the Cikarang and Bekasi rivers, with a combined drainage area of 2,000 km2 which are also connected with the Citarum river through the West Tarum Canal. Together, these inter-connected river basins make up the Citarum river basin territory (program area). The area is a key rice producer for the country. There are a total of 390,000 ha of irrigated rice paddies, with 240,000 ha served by the Juanda reservoir and canal system in the lower basin. Also within the program area are three large dams that generate a total of 1,400 megawatts, and major industries centered at Bandung and the rapidly urbanizing corridor east of Jakarta (Bekasi-Cikarang). Forest areas in the upper Citarum have declined from 35,000 ha in 1992 to 19,000 ha in 2001. Remaining forests cover only about 10.2% of the program area.
The numerous environmental issues in the CRB result predominantly but not exclusively from the same urbanization and industrialization that is the cause of water supply shortages. Deforestation of the upper catchments cause increased sediment loads, flash floods, landslides, and other water-related disasters. The potential effects of climate change have yet to be quantified. The combination of untreated domestic sewage, solid waste disposal, and industrial effluents has significantly increased pollution loads in the Citarum River system. In the upper basin, river water polluted with domestic and industrial waste from Bandung flows into the Saguling Reservoir. Biological oxygen demand10 at the Saguling Reservoir inlet reaches as high as 130 milligrams per liter (mg/l) during the dry season. In recent years, biological oxygen demand in the Cikapunding River a major tributary of the Saguling River, which flows through Bandung was reported to reach as high as 100 mg/l. Inadequate sanitation and solid waste management are problems in urban, peri-urban, and rural communities. These problems degrade not only the environment but also community health and living standards.
Runoff from hillside farms contributes significant amounts of the nutrients nitrogen and phosphorus, which induce eutrophication in the reservoirs. At Saguling, where the problem is most significant, nitrogen loading is estimated at over 33,000 tons per year, and phosphorus loading at 4,370 tons per year. Algal blooms and their subsequent decay regularly cause fish kills, inflicting considerable financial losses to fish farmers. Hydrologic flow regimes have been adversely changed by land degradation, notably the loss of adequate forest cover and the prevalence of hillside farming in upper catchments. The degraded catchments have reduced capacity to capture rainwater, causing high peak flows during the rainy months that carry large amounts of eroded soil. At the entrance to the Saguling Reservoir, the ratio of the volume of wet season high flows to dry season low flows has increased from 3.4 in 1992 to 7.4 in 2003. As a result, landslides and mud flows are frequent during the rainy season. An estimated 25% of the basin now suffers erosion in excess of 60 tons per ha per year, or 3 4 millimeters of soil loss annually.
The CRB is experiencing the shrinkage of natural ecosystem areas, notably forested
areas. Recent West Java reports on the environmental state of the basin show ecological diversity in the CRB, which has 160 plant species, 24 mammals (20 protected, 3 endemic, and 1 scarce), 72 birds (60 protected, 10 endemic, and 2 scarce), 11 protected reptiles, and 2 protected fish. Land-use changes have left only scattered remnants of natural forest habitat. Much of it is in the 240,402 ha of 11 protected forest areas, which are significant for the conservation of biodiversity because they are among the most intact areas of forest remaining on Java. Most of the protected areas were relatively undisturbed when designated. However, in recent times many have suffered serious degradation as a result of encroachment, the illegal removal of non-timber forest products, fires, and illegal logging. All remaining patches of natural vegetation in the CRB, even if secondary, are of the highest conservation significance.